1. Field of the Invention
The present invention relates to the field of aerodynamics, and more particularly to methods and apparatus for the operation of aircraft at higher angles of attack and coefficients of lift, particularly when taking off and landing.
2. Prior Art
A modern high performance jet aircraft of simple configuration typically is comprised of a fuselage, swept back wings of a delta or trapezoidal configuration, and horizontal and vertical tail surfaces. Typically such basic configurations perform relatively well, though frequently it is desired to improve certain aspects of operation or performance thereof. Two aspects frequently sought to be improved are operation at lower speeds and higher angles of attack, and the enhancement of the stability and control of the aircraft.
Wing lift has also been increased in the past by adding a leading edge extension to the wings in the root area. While this somewhat increases the wing area, it also allows operation of the aircraft at higher angles of attack, thereby primarily increasing the coefficient of lift for the wing through an increase in the angle of attack. Such leading edge extensions typically are in the plane of the wing, and simply extend the wing forward in the root area thereof.
In still other situations, strakes have been used for various purposes, sometimes only fully appreciated by the designers that added the same to the basic aircraft configuration, the strakes correcting some undesired local flow or somehow controlling the flow to obtain some desired effect not otherwise inherent in the basic aircraft configuration. By way of specific example, the Mirage 2000, a French delta wing aircraft, has a small strake above and just forward of the wing root, the purpose of which is not apparent as the same is too small for any meaningful lift enhancement. A similar small strake appears on an Israeli modification of the Mirage, a delta wing aircraft as well. Similar strakes have heretofore not been used on trapezoidal wing aircraft. On the other hand, on the McDonnell Douglas MD-80 commercial airliner, small wing-like strakes are positioned well forward on the fuselage, much like a Canard configuration. On the DC-10, strakes are used on the engine housings under the wings thereof.
Finally, Northrop has demonstrated that a strake of significant size could be attached to the wing of a trapezoidal wing aircraft to extend the operation of the aircraft to higher angles of attack, yielding higher coefficients of lift. In essence such strakes locally extend the wing forward as in a leading edge extension. In the case of the present invention, however, it has been found that by moving the strakes to a position out of the plane of the wing, specifically to a position above the wing just forward thereof, similar increases in the angle of attack and coefficient lift of the aircraft may be achieved, though with improved pitch stability of the aircraft in comparison to the positioning of the same in the plane of the wings.